小主带小行星的光度测量和自转速率分布
Photometry and Spin Rate Distribution of Small-Sized Main Belt Asteroids
摘要：
32颗小行星的光度测定结果仅在7个观测场的7个观测夜晚报告，包括34.11小时的累积观测。这些数据是由安装在Wise天文台一台46厘米小型望远镜上的宽视场CCD（40.5 'x27.3'）获得的。这些区域位于黄道面1.5度以内，包括主小行星带内的一个区域。观测场显示，在我们观测的极限范围内，预计每平方度约有23.7颗小行星。其中13个光变曲线被成功地分析，以得出小行星的自转周期。这些时间范围为2.37至20.2小时，中位数为3.7小时。其中11个天体的直径在2公里或更小，直到最近才进行光度学研究。在这一短期观测运行期间获得的结果强调了小行星宽视场CCD测光的效率，这对于改进自旋统计和了解自旋演化过程是必要的。我们将我们推导出的自转周期与文献中的数据相加，并将主带小行星（5>D>0.15公里）的自转率分布与较大的小行星和类似大小的近地小行星的自转率分布进行了比较。我们发现，小MBA并不像大的小行星那样显示出清晰的麦克斯韦形分布;相反，它们的自旋速率分布与近地小行星相似。这意味着非麦克斯韦的自旋速率分布是由小行星的大小而不是它们的位置控制的。
英文摘要：
Photometry results of 32 asteroids are reported from only seven observing nights on only seven fields, consisting of 34.11 cumulative hours of observations. The data were obtained with a wide-field CCD (40.5'x27.3') mounted on a small, 46-cm telescope at the Wise Observatory. The fields are located within 1.5 degrees from the ecliptic plane and include a region within the main asteroid belt. The observed fields show a projected density of ~23.7 asteroids per square degree to the limit of our observations. 13 of the lightcurves were successfully analyzed to derive the asteroids' spin periods. These range from 2.37 up to 20.2 hours with a median value of 3.7 hours. 11 of these objects have diameters in order of two km and less, a size range that until recently has not been photometrically studied. The results obtained during this short observing run emphasize the efficiency of wide-field CCD photometry of asteroids, which is necessary to improve spin statistics and understand spin evolution processes. We added our derived spin periods to data from the literature and compared the spin rate distributions of small main belt asteroids (5>D>0.15 km) with that of bigger asteroids and of similar-sized NEAs. We found that the small MBAs do not show the clear Maxwellian-shaped distribution as large asteroids do; rather they have a spin rate distribution similar to that of NEAs. This implies that non-Maxwellian spin rate distribution is controlled by the asteroids' sizes rather than their locations.
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